The present invention relates to a printing apparatus, and in particular, to a printing apparatus wherein a thermal head is compressed, via an ink ribbon accommodated in a cartridge, against a card, the one side of which is supported by a platen roller, to print an image on the card.
A printing apparatus is conventionally known, wherein a thermal head is compressed, via an ink ribbon, against a print sheet, the one side of which is supported by a platen roller, to print an image on the print sheet. In the printing apparatus, when the compression of the thermal head is canceled after completion of printing, the ink ribbon becomes slack to bring the ink ribbon into contact with the platen roller. In this condition, feeding or insertion of a print sheet may displace the slack ribbon from a front surface of the thermal head to prevent normal printing. Such a configuration is disclosed in Japanese Patent Application Publication No. 60-56584. Furthermore, in this condition, rotation of the platen roller may cause the ink ribbon to twine around the platen roller owing to static electricity. Such a configuration is disclosed in, for example, Japanese Utility Model Application Publication No. 06-45744.
Thus, to solve this problem, the slack ink ribbon needs to be taken up and separated from the platen roller. Both Japanese Patent Application Publication No. 60-56584 and Japanese Utility Model Application Publication No. 06-45744 disclose a technique of taking up the slack ink ribbon. Although Japanese Utility Model Application Publication No. 06-45744 prevents the slack ink ribbon from twining around a drum owing to the static electricity, the two techniques are the same in that the ink ribbon is prevented from twining around a rotating member owing to static electricity.
However, with a printing apparatus using a plurality of color ink ribbons, for example, Y (Yellow), M (Magenta), C (Cyan), Bk (Black), and Op (protect layer) may be sequentially printed in this order. In this case, a next color ink ribbon needs to be registered. Registration of the ribbon is such that for example, if printing of the Y color is followed by printing of the M color, the ink ribbon is fed (taken up) from a print end position for the Y color to a print start position for the M color to align a predetermined position on the ink ribbon with the print start position for the M color.
However, the amount by which the ribbon is fed during registration is not always constant. For example, if the card has been printed to the half thereof, the distance over which the ribbon needs to be fed for registration increases. In contrast, if the card has been entirely printed, the distance over which the ribbon needs to be fed decreases. Furthermore, the ink ribbon for Y includes a marker provided at a leading end thereof to register the ribbon. Thus, the printing of the ink ribbon for Y needs to be started from a more backward position than that of the ink ribbons for the other colors. Consequently, the distance from the print end position for the Y color to the print start position for the M color may decrease, thus reducing the distance over which the ribbon is fed for registration.
Moreover, the above marker may be provided between the M color and the C color within a predetermined image surface. This further reduces the distance from the print end position for the Y color to the print start position for the M color (see FIG. 10). Therefore, simply taking up the slack ink ribbon may displace the ink ribbon to affect the next color printing.
In view of these circumstances, an object of the present invention is to provide a printing apparatus and a ribbon registering method which enable the ink ribbon to be controllably registered according to the distance over which the ink ribbon is taken up to eliminate a slack in the ink ribbon having been slack as a result of printing and the distance from the print start position to the print start position for the next color.
Further objects and advantages of the invention will be apparent from the following description of the invention.